Brushless motor and method of manufacturing the brushless motor

ABSTRACT

A brushless motor, comprising a rotor having a magnet, a coil for generating a magnetic field for drivingly rotating the rotor, and a power supply terminal for supplying a power to the coil from outside, wherein all electrical connection parts ranging from the power supply terminal to the end of the coil are connected to each other through welded parts.

TECHNICAL FIELD

[0001] The present invention mainly relates to a small brushless motorsuitably used for portable electronic equipment and a method ofmanufacturing the same, and particularly concerns a wire treatmenttechnique of its coil.

BACKGROUND ART

[0002] In a process of connecting the ends of coils to external powersupply terminals in a small brushless motor, in general, wire treatmentis performed using terminals and a treated part is soldered to haveelectric conduction.

[0003] For instance, a representative example is disclosed inJP-A-6-46543. In this example, a core has a plurality of salient polesextending radially from a ring part and coils are wound around thesalient poles. Further, slots between the salient poles have terminals,and the ends of coils are connected to the terminals by winding. Theterminals have coil end winding portions which are formed so as to bebent in the axial direction of the core and can be soldered ontoexternal power supply terminals, each being arranged at a position onone side of the coil along the axial direction of the core. Suchterminals are often used for small brushless motors.

[0004] Another publicly known technique is disclosed in JP-A-4-193053.Conventionally, a resin-molded insulator has been frequently placed onan end face of a core to secure insulation between the core and a coil.In such a publicly known technique, a terminal of a thin metallic plateis embedded into a part of the insulator, the part corresponding to asalient pole. Then, the coil is wound and held so as to bind the salientpole and the terminal. A coil end winding portion on the end of theterminal is formed so as to be bent in the axial direction and issoldered onto a printed wiring board which is adjacent to one side ofthe coil. With such a configuration, since the terminals are held by thesalient poles, even thin and small terminals can be correctly positionedand soldered on external power supply terminals.

[0005] In the case of electronic equipment, when an electronic componentis mounted on a printed board, soldering is performed according to amethod of dipping into a soldering bath, a method of melting creamsolder by reflow heating, and so on. However, as global environmentalpollution has been a focus of attention in recent years, lead containedin a soldering material has become controversial. For this reason, in acomponent mounting process, a soldering material containing lead hasbeen converted to a lead-free soldering material. The same demand ismade on motors and conversion is demanded to a lead-free solderingmaterial or a method of using no soldering material.

[0006] In response to such a demand, a lead-free soldering material maybe selected. However, there is another factor that forces conversion toa joining method using no soldering material. For example, in a motorconfigured such that reflow mounting can be made on a substrate of amobile phone, when a soldered part exists in the motor, heat of reflowheating is conducted to the soldered part and causes melting againbecause the motor is quite small. Such a problem has not been found inconventional motors which have not been devised based on reflowmounting. However, this problem is expected to be a significant problemto be solved for microminiature motors which will increase in number. Inorder to respond to this problem, conversion should be made to a joiningmethod using no soldering material.

[0007] As a method of making electrical connection using no solderingmaterial on a wire-treated part of winding, for example, a fusing methoddisclosed in JP-A-63-228937 has been known. In this technique, aterminal is adjacent to a coil wound around a core and has a hook. Thewinding terminal of the coil is connected to the terminal via the hook,and then, joining is performed by heating the hook by energization andapplying pressure thereon.

[0008] However, the fusing method requires a large vacant space aroundthe terminal. This is because it is necessary to pass a tool for heatingby energization while sandwiching the hook of the terminal between bothsides and applying pressure thereon. Therefore, this method is notapplicable to a small and high-density motor which does not have asufficient space around a terminal.

SUMMARY OF THE INVENTION

[0009] Thus, the present invention has an object to provide a wiretreatment technique which can make electrical connection without using asoldering material even when a terminal is used but a sufficient spacecannot be obtained around the terminal in a brushless motor, therebyachieving a small brushless motor which causes little environmentalpollution and prevents reheating of reflow mounting or the like fromdegrading the quality.

[0010] In order to attain the above object, a brushless motor of thepresent invention comprises a rotor having a magnet, a coil forgenerating a magnetic field for rotatively driving the rotor, and apower supply terminal for supplying a power to the coil from outside,wherein all electrical connection portions ranging from the power supplyterminal to the end of the coil are joined by welding.

[0011] Further, the brushless motor of the present invention comprises arotor having a magnet, a coil for generating a magnetic field forrotatively driving the rotor, a core for winding the coil, and aplurality of terminals composed of metallic members, wherein the corehas a ring part and a plurality of salient poles extending radially fromthe ring part, the coil being wound around the salient pole, theterminal has a metal exposure surface for connecting an earth electrodefor welding, and the end of the coil is connected to the terminal bywinding and then the end is joined by arc welding.

[0012] With this configuration, since all the electrical connectionportions ranging from the end of the coil to the power supply terminalare joined by welding, or since the end of the coil is connected to theterminal by winding and then the end is joined by arc welding, it ispossible to obtain a reliable motor which can eliminate solder on theelectrical connection portions with little environmental pollution anddoes not degrade the quality of the electrical connection portions evenin the case of severe temperature environments for mounting and use.Moreover, to make electrical connection, means of caulking, crimping,screwing, and so on are available in addition to soldering and welding.In each of these means, a connecting structure occupies a large space.Unlike these means, welding makes the connecting structure to occupy asmall space equivalent to a space required by soldering. Hence, it ispossible to provide a small and reliable brushless motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a sectional view showing a structure of a brushlessmotor according to Embodiment 1 of the present invention;

[0014]FIG. 2 is a diagram showing that terminals of FIG. 1 are connectedvia a connecting member;

[0015]FIG. 3 is a diagram showing a state in which a configuration ofFIG. 2 is overlaid on a core;

[0016]FIG. 4 is a diagram showing a state in which coils are wound inthe configuration of FIG. 3;

[0017]FIG. 5 is a diagram showing a state in which terminals and ends ofcoils of FIG. 4 are joined by arc welding;

[0018]FIG. 6 is a diagram for describing that a connecting member ofFIG. 5 is cut and removed;

[0019]FIG. 7 is a diagram showing a state in which arc welded junctionsof FIG. 6 are resistance-welded to power supply terminals;

[0020]FIG. 8 is a diagram showing that terminals for manufacturing abrushless motor according to Embodiment 2 of the present invention areconnected via a connecting member;

[0021]FIG. 9 is a diagram for describing that the connecting member iscut and removed after the configuration of FIG. 8 is overlaid on a core;

[0022]FIG. 10 is a diagram for describing that coils are wound in aconfiguration of FIG. 9 and terminals and the ends of coils are joinedby arc welding;

[0023]FIG. 11 is a diagram showing a stator assembly of a motoraccording to a first conventional art;

[0024]FIG. 12 is a diagram showing an insulator of a motor according toa second conventional art; and

[0025]FIG. 13 is a perspective view showing a stator assembly of a motoraccording to a third conventional art.

Preferred Embodiments DESCRIPTION OF THE PRIOR ART

[0026] Prior to description of embodiments of the present invention, forreference, examples of publicly known brushless motors will be discussedin accordance with FIGS. 11 to 13.

[0027] Referring to FIG. 11, the technique disclosed in JP-A-6-46543will be discussed below. In this example, a core 101 has a plurality ofsalient poles 103 extending radially from a ring part 102 and coils 104are wound around the salient poles 103. Slots between the salient poles103 have terminals 105, and coil ends 106 are connected to the terminals105 by winding. The terminals 105 have coil end winding portions whichare formed so as to be bent in the axial direction of the core 101 andcan be soldered onto external power supply terminals 107, (in this case,lands on a flexible printed circuit board 108), each being placed at aposition on one side of the coil 104 along the axial direction of thecore 101.

[0028] The technique disclosed in JP-A-4-193053 is shown in FIG. 12.FIG. 12(a) is a sectional view taken along a line B-B of FIG. 12(b).Conventionally, a resin-molded insulator has been frequently placed onan end face of a core to secure insulation between the core and a coil.In this case, a terminal 112 of a thin metallic plate is embedded into apart of an insulator 111, the part corresponding to a salient pole 114.Then, a coil (not shown) is wound and held so as to bind the salientpole 114 and the terminal 112. A coil end winding portion 113 on the endof the terminal 112 is formed so as to be bent in the axial directionand is soldered on a printed wiring board (external power supplyterminals provided thereon any of them is not shown) which is adjacentto one side of the coil. With such a configuration, since the terminals112 are held by the salient poles 114, even thin and small terminals canbe correctly positioned and soldered on external power supply terminals.

[0029]FIG. 13 shows the fusing method disclosed in JP-A-63-228937. Inthis method, a terminal 121 is adjacent to coils 123 wound around a core122 and has a hook 124. A end of coil winding 125 is connected to theterminal 121 via the hook 124 and joining is performed by heating thehook 124 by energization and applying pressure thereon.

[0030] However, the fusing method requires a large vacant space aroundthe terminal 121. This is because it is necessary to pass a tool forheating by energization while sandwiching the hook 124 of the terminal121 between both sides and applying pressure thereon. Therefore, thismethod is not applicable to a small and high-density motor which doesnot have a sufficient space around a terminal.

DESCRIPTION OF EMBODIMENT OF THE PRESENT INVENTION

[0031] The present invention is achieved to solve the problem of theconventional art. The following will discuss the embodiments inaccordance of the accompanied drawings.

[0032] (Embodiment 1)

[0033] For example, a motor shown in FIGS. 1 to 7 is a brushless motorwhich is extremely small and thin with an external diameter of about 10mm. Such a motor is used for vibration alerm in a mobile phone and soon. In FIG. 1, the motor is constituted by a stator (non-rotating part)1, a rotor (rotary part) 2, and a cover 18. The rotor 2 has a rotorframe 11 as a main body, and a ring-shaped magnet 12 is attached to theinside of the rotor frame 11. An eccentric weight 13 is attached to therotor frame 11. The rotor frame 11 rotates around a shaft 14 mounted atthe center of the rotor frame 11.

[0034] The stator 1 has a motor base 15 as a main body. A windingassembly composed of a core 21, coils 22, and terminals 31 is mounted onthe motor base 15, and a metal 16 for supporting the shaft 14 is furthermounted at the center of the motor base 15. Coil ends 23 are connectedto power supply terminals 17 of the motor base 15. Moreover, asdescribed above, the shaft 14 of the rotor 2 is rotatively fit into themetal 16 and is covered with a cover 18 shaped like a cap. The powersupply terminal 17 is exposed on the lower surface of the motor so as tomake reflow connection on a board (not shown) of equipment.

[0035] The completed motor makes reflow connection on the board of theequipment (mobile phone) as described above and power is applied to thecoils 22 via the metallic power supply terminals 17 on the lowersurface, so that the rotor 2 rotates. Then, the eccentric weight 13attached to the rotor 2 generates vibration so as to vibrate theequipment.

[0036] Since the present invention relates to the structure of thestator 1, the detail of the stator 1 will be discussed below.

[0037]FIG. 2 shows the shape of the terminals. In this case, the sixterminals 31 are arranged radially and are integrally connected via aconnecting member 32 placed at the center. The connecting member 32 hasa positioning hole 32 a penetrating at the center.

[0038] Each of the terminals 31 has a wide base serving as a holdingportion 31 a, which overlaps the salient pole of the core and an endserving as a coil end connection portion 31 b. Further, as describedabove, the terminals 31 are connected to one another at the holdingportions 31 a via the connecting member 32 and maintain their positions.Between the holding portion 31 a and the coil end connection portion 31b on each of the terminals 31, two bent portions 31 c, 31 c are formedlike a letter Z. Thus, the coil end connection portion 31 b is shiftedfrom the holding portion 31 a in the axial direction of the motor. Onthe way to the connecting member 32 from the holding portion 31 a, amember 31 f integrally extends in the rotating direction of the motor,and the end of the member 31 f is bent in the axial direction of themotor to form a crossover wire guide 31 d.

[0039] The terminals 31 are formed by using a nonmagnetic metal, thatis, a copper alloy plate such as a thin phosphor bronze plate with athickness of about 80 μm. Then, an insulation coating 31 e made of amaterial such as an ultraviolet curing resin and a thermosetting resinis formed on a part of the surface of the terminal 31. In FIG. 2(a),regions indicated by hatching of broken lines represent the insulationcoatings 31 e. As shown in FIG. 2(a), the insulation coatings 31 e areformed on the inside of the bent portions 31 c in the diameter directionand on the outside of the connecting member 32 in the diameterdirection. Namely, insulation is not made on the bent portions 31 c, thecoil end connection portions 31 b, and the connecting member 32.

[0040] For example, the insulation coatings 31 e can be formed byevaporation of a polyimide material when a thickness is placed at thehighest priority. With this evaporation, a thickness of several μm isapplicable. However, the thickness needs to be not less than 3 μm inorder to provide withstand voltage of about 300V for the insulationcoatings. In FIG. 2, since emphasis is placed on productivity, a coatingwith a thickness of 10 to 30 μm is formed according to a method ofapplying and curing a liquid thermal setting resin by screen printing.Further, when priority is placed on withstand voltage and reliability onheat resistance that include a burr formed in a shearing process, acoating with a thickness of about 100 μm may be formed by increasing athickness of a mask screen or controlling a viscosity of liquid.Therefore, it is preferable that the insulating coatings 31 e are each 3to 100 μm in thickness.

[0041]FIG. 3 shows a state in which the terminals 31 are overlaid on thesurface of the core 21. The core 21 has a ring part 21 a placed aroundat the center and six salient poles 21 b radially extending outward fromthe ring part 21 a. The terminals 31 are placed in contact with thesalient poles 21 b of the core and are temporarily fixed by adhesive andso on. At this moment, the terminal 31 has a thickness of about 0.1 mmincluding the insulation coating and the motor has a small increase inthickness.

[0042] The configurations of the terminals 31 will be discussed again inassociation with the core 21. The coil end connection portions 31 b areseparated from the surface of the core 21 in the axial direction of themotor by the bent portions 31 c and the coil end connection portions 31b extend radially in parallel with the surface of the core. The bentportions 31 c are positioned in the vicinity of an outer circumferentialsurface 21 c of the core and do not protrude outward from the outercircumferential surface 21 c in the diameter direction. The connectingmember 32 is placed inside the ring part 21 a of the core. The members31 f extend over the ring part 21 a from the holding portions 31 a ofthe terminals 31, and the crossover wire guides 31 d protrude in theaxial direction of the motor at the center between the salient poles 21b.

[0043]FIG. 4 shows a state in which the coils 22 are wound in theconfiguration of FIG. 3. In this case, the motor is a three-phasebrushless motor and has three pairs of the coils 22 (and salient poles21 b). In FIG. 4(a), for example, the coils 22 are wound around thesalient pole 21 b on the right end of FIG. 4(a), a crossover wire 24 isrouted counterclockwise while being guided by a plurality of thecrossover wire guides 31 d, and the crossover wire 24 is wound aroundthe salient pole 21 b on the left end. The coil ends 23 are wound aroundthe coil end connection portions 31 b placed near the ends of thesalient poles 21 b. The above operation is repeated for three times onthree points, so that assembling is completed as shown in FIG. 4(a).

[0044] At this moment, the insulation coating 31 e of the terminal isformed so as to cover a part of the terminal 31, the part being incontact with the coil 22 and the crossover wire 24, so that insulationis maintained between the terminal 31 and the coil 22. The terminal 31is in contact with the core 21 as well as the coils 22. Insulation canbe similarly obtained by forming the insulation coatings on the core 21.Therefore, in this case, insulation is not always necessary on a part ofthe terminal 31 that is in contact with the core 21.

[0045] Next, the coil ends 23 are joined to the coil end connectionportions 31 b by arc welding. First, as shown in FIG. 4(b), an earthelectrode 71 of a welding machine is electrically connected to theconnecting member 32 at the center of the terminals 31. To be specific,the earth electrode 71 is pressed onto the positioning hole 32 a whichis formed at a center of the connecting member 32, that is, near thering part 21 a of the core 21 and serves as a metal exposure surface.Regarding the plurality of terminals 31, the metal exposure surfaceformed by the positioning hole 32 a is placed substantially at equaldistances from the center of the core 21. A welding electrode 72 isopposed to the end of the coil end connection portion 31 b. Then, arcdischarge is generated and the coil ends 23 and the coil end connectionportions 31 b are fused and joined to each other. This operation isperformed for six times while the core 21 is rotated by 60°, so thatwelding is completed. A nonconsumable electrode made of a material suchas tungsten is used as the welding electrode 72. A fused portion iscovered with inert gas which contains argon and is discharged from a gap77 on the outer circumference of the welding electrode 72, so thatoxidation is prevented. FIG. 5 shows a state in which welding iscompleted. The base materials of the coil end connection portions 31 bare fused and joined so as to cover the coil ends 23. Reference numeral31 h denotes arc welded junctions of the coil end connection portions.

[0046] Next, as shown in FIG. 6, the connecting member 32 at the centeris cut and removed by a cutting tool 73. In FIG. 6, a cut portion, thatis, an inner circumferential end 31 g slightly protrudes to the insideof the ring part 21 a. The cutting tool 73 is operated while beingguided near the ring part 21 a of the core, and the remaining protrusionis minimized. Or the following application is possible: the cut portion31 g is protruded, is engaged to the motor base 15, and is held in theaxial direction or the rotating direction.

[0047] A winding assembly completed thus is mounted on the motor base15. This state is shown in FIG. 7. The arc welded junction 31 h of theterminal 31 is overlaid on the power supply terminal 17 of the motorbase 15. When this portion is interposed between resistance weldingheads 76 and current is applied, heat is generated by Joule heat. Whenheating is generated and pressure is applied just before dissolution,the arc welded junction, that is, the fused coil end connection portion31 b and the power supply terminal 17 are welded. Then, assembling isperformed as described at the beginning so as to complete the motor.

[0048] In this way, the plurality of terminals 31 is connected via theconnecting member 32, the earth electrode 71 is connected to theconnecting member 32, the coil ends 23 are joined by arc welding, andthen, the connecting member 32 is cut and removed, so that the pluralityof terminals 31 can be collectively subjected to arc welding. At thismoment, in the case of spot heating such as a laser beam, a heated andmelted region is small and breaks may occur on the coils. In the case ofarc welding, after the coil ends 23 are connected to the ends of theterminals 31 by winding, the base materials of the terminals 31 aremelted to perform joining so as to cover the coil ends 23. Therefore,the quality of joining by arc welding is stabilized without apossibility of breaks on the coils. Further, the connection portions ofthe coil ends 23 are smaller than those of fusing and can be joined bythe terminals of low rigidity. Besides, joining by arc welding can beperformed in smaller working area than that of fusing. Since the earthelectrode 71 is connected to the cut and removed region, arc welding canbe performed on a microminiature motor which cannot be provided with awide metal exposure surface.

[0049] The terminals 31 formed of metallic members are arranged on oneof the surfaces on the core 21 along the axial direction of the motor,so that the metal exposure surface for connecting the earth electrode 71can be provided in an advantageous manner. This is because a relativelywide metal exposure surface can be readily formed by using the ring part21 a of the core 21 or a vacant space around the ring part 21 a.Moreover, when the earth electrode 71 is connected to the terminals 31in a collective manner, axial access is the easiest way to have accessto all the terminals 31 simultaneously.

[0050] The terminals 31 have the inner circumferential ends 31 g whichprotrude inward more than the ring part 21 a of the core. Namely, theterminals 31 protrude inward of the core 21 or the edges of the coils 22in the axial direction of the motor. Hence, in the case of the method ofcutting and removing the connecting member 32 after arc welding, acutting tool can be readily inserted with high workability.

[0051] Between the holding portion 31 a and the coil end connectionportion 31 b, the terminal 31 has the bent portions 31 c, 31 c arrangedin the axial direction of the motor. On this point, the outercircumferences of the salient poles 21 b and the magnet 12 are close toeach other and the terminals 31 held by the salient poles 21 b are alsoclose to the magnet 12 in a motor of outer rotor type. Since the bentportions 31 c, 31 c are provided thus, it is possible to prevent theterminals 31 and the magnet 12 from being in contact with each other. Inaddition, it is possible to guide the coil end connection portions 31 bto positions where the external power supply terminals 17 can be readilypositioned and connected. Further, it is possible to increase a distancebetween the arc welding part and the coil main body, thereby reducingadverse effect such as welding heat on the coils 22.

[0052] The coil end connection portions 31 b of the terminals 31 areformed perpendicularly to the motor shaft. Thus, even when the length ofthe junction is varied in the welding process, the positionalrelationship with the power supply terminals 17 is not changed.

[0053] The terminals 31 have parts protruding outward of the peripheryof the core 21 or the edges of the coils 22 in the axial direction ofthe motor at different positions from the connection portions of thecoil ends 23. Hence, in the case of the method of cutting and removingthe connecting member 32 after arc welding, it is possible to readilypass a cutting tool with high workability.

[0054] The arc welded junctions 31 h are resistance-welded to the powersupply terminals 17, and the arc welded junctions 31 h are substantiallyshaped like spheres as shown in the drawings, thereby fixing the weldingconditions of resistance welding. Thus, it is possible to eliminate thenecessity for a soldering material on the connection between theterminals 31 and the coil end connection portions 31 b as well as theconnection between the terminals 31 and the power supply terminals 17.

[0055] The terminals 31 are made of a copper alloy, which belongs to thesame system as that of the coil 22, thereby achieving preferable qualityof joining on a welded connection.

[0056] Since the arc welded junctions 31 h are positioned outside thecore 21 and the edges of the coils 22 in the axial direction of themotor, it is possible to arrange the terminal connection portions of theterminals outside the core 21 and the edges of the coils 22 in thediameter direction. Thus, the resistance welding heads 76 can be readilybrought close to each other along the axial direction of the motor and aconnecting operation can be readily performed.

[0057] The metal exposure surface for the plurality of terminals 31 ispositioned substantially at equal distances from the center of the core21, the metal exposure surface being formed by the positioning hole 32a. Hence, the same earth electrode can be used for all the terminals 31.Moreover, the ring-shaped earth electrode is used which is positioned onthe same axis as the center of the core 21, and welding can be performedwhile rotating and transporting a work.

[0058] As described above, in the motor of Embodiment 1, the powersupply terminals 17 can be reflow-mounted on a board of equipment andall the electrical connection portions from the power supply terminalsto the coil ends are joined by welding. Hence, even when heat of reflowheating is conducted during reflow mounting of the motor into theequipment, it is possible to achieve a microminiature brushless motorwithout degradation in quality of the electrical connection portions andthe product.

[0059] (Embodiment 2)

[0060] Referring to FIGS. 8 to 10, the following will discuss Embodiment2 of the present invention. In Embodiment 2, the connecting structure ofterminals 51 is changed from that of Embodiment 1 and the manufacturingprocess is changed accordingly. In the following description, drawingsand explanations which are redundant or the same as Embodiment 1 will beomitted.

[0061]FIG. 8 shows the shapes of the terminals 51. The six terminals 51are arranged radially and are integrally connected to one another via aframe-shaped connecting member 52 which is placed outside the terminals51. On each of the terminals 51, a base portion formed inside along theradial direction is a holding portion 51 a which is overlaid on asalient pole of a core, and an end formed outside along the radialdirection is a coil end connection portion 51 b. Then, as describedabove, the coil end connection portions 51 b are connected via theconnecting member 52 and maintain their positions. Two bent portions 51c are placed between the holding portion 51 a and the coil endconnection portion 51 b so that the coil end connection portions 51 bare shifted in the axial direction of the motor. Reference numeral 51 ddenotes guides for a crossover wire. The guides are formed on the endsof members 51 f. An insulation coating 51 e is formed on a part of thesurface of the terminal 51. In FIG. 8(a), regions indicated by hatchingof broken lines represent the insulation coatings 51 e. On the terminal51, the insulation coating is not formed on an inner circumferential end51 g, which is overlaid on a ring part 41 a (FIG. 9) of a core 41, and ametallic surface remains exposed thereon.

[0062]FIG. 9 shows that the terminals 51 are overlaid on the surface ofthe core 41. As shown in FIG. 9, the terminals 51 are placed in contactwith salient poles 41 b of the core 41 and are fixed by adhesive and soon. Next, the connecting member 52 is cut and removed from the terminals51. At this moment, cutting is made by using a cutting tool 74 of FIG. 9on ends 51 h of the coil end connection portions 51 b.

[0063]FIG. 10 shows a state in which coils 22 are wound after theconnecting member 52 is cut and removed thus. As with Embodiment 1, theprocess is repeated for three times to complete a winding operation.Next, the coil end connection portions 51 b and coil ends 23 are joinedto each other by arc welding. First, an earth electrode 75 of a weldingmachine is electrically connected to metal exposure surfaces on theinnermost circumference of the terminal, that is, the innercircumferences 51 g. In order to make such connection, the earthelectrode 75 shown in FIG. 10(b) is used. The earth electrode 75 isformed by externally fitting a ring-shaped electrode 75 b onto a guidebar 75 a which is fit into a positioning hole 41 c on the innermostcircumference of the core 41. The earth electrode 75 is pressed onto themetal exposure surfaces of the terminals 51, that is, the innercircumferences 51 g. A welding electrode 72 is opposed to the end of thecoil end connection portion 51 b. Then, arc discharge is generated tojoin the coil end connections portions 51 b and the coil ends 23 bywelding. This operation is performed for six times while rotating thecore 41 by 60°, so that welding is completed.

[0064] A winding assembly completed thus is placed on a motor base as inthe case of Embodiment 1 and the coil end connection portions 51 b ofthe terminals 51 are connected to power supply terminals, so that themotor is completed.

[0065] In this way, the metal exposure surface 51 g that can connect theearth electrode 75 for welding is provided on a part of the terminal 51,and joining is performed by arc welding after the coil ends 23 areconnected to ends 31 b of the terminals by winding. Hence, the coil endconnection portions 31 b can be joined by the terminals 51 which aresmaller than those of fusing and can be joined by the terminals 51 oflow rigidity. Besides, joining can be performed in a smaller workingarea than that of fusing.

[0066] Since the metal exposure surfaces 51 g of the terminals 51 areclose to the ring part 41 a of the core 41, even thin and weak terminalsof a microminiature motor can be supported by the ring part 41 a whenthe earth electrode is connected, achieving a stable operation.

[0067] The metal exposure surfaces 51 g of the terminals 51 are arrangedon the surface of the core 41 in the axial direction of the motor. Whenthe earth electrode 75 is connected to the terminals 51 in a collectivemanner, axial access is the easiest way to have access to all theterminals 51 simultaneously.

[0068] Since the metal exposure surfaces 51 g of all the terminals 51are positioned at equal distances from the center of the core 41,welding can be performed by using the ring-shaped earth electrode 75,which is positioned on the same axis as the center of the core 41, whilea work is rotated and transported.

[0069] The above explanations discussed some embodiments of the presentinvention. The present invention should not be limited to theabove-described embodiments and various applications are acceptablewithin the scope of the present invention. For example, the aboveembodiments only discussed the case where the thin-plate terminals 31and 51 are held by the salient poles 21 b and 41 b of the cores 21 and41. The present invention is applicable to other structures. Forexample, terminals using square pins may be held by a ring part of acore. Even when the core is not provided, the effect of joining all theelectric connection portions by welding can be exerted.

What is claimed is:
 1. A brushless motor, comprising: a rotor having amagnet; a coil for generating a magnetic field for rotatively drivingthe rotor; and a power supply terminal for supplying a power to the coilfrom outside, wherein all electrical connection portions ranging fromthe power supply terminal to an end of the coil are joined by welding.2. The brushless motor according to claim 1, wherein said power supplyterminal has an end which is exposed on a bottom of the motor and can bereflow-mounted on aboard of equipment.
 3. A brushless motor, comprising:a rotor having a magnet; a coil for generating a magnetic field forrotatively driving the rotor; a core for winding the coil; and aplurality of power supply terminals composed of metallic members,wherein the core has a ring part and a plurality of salient polesextending radially from the ring part, the coil being wound around thesalient pole, each terminal has a metal exposure surface for connectingan earth electrode for welding, and an end of the coil is connected tothe terminal by winding and then the end is joined by arc welding. 4.The brushless motor according to claim 3, wherein the terminals arearranged on one of surfaces on the core along an axial direction of themotor.
 5. The brushless motor according to claim 3, wherein the terminalhas a coil end connection portion for connecting the end of the coil bywinding, the plurality of terminals are arranged, in advance, to extendradially and connect to each other via a connecting member at adifferent portion from the coil end connection portion, and theconnecting member is cut and removed from the terminals after the coilend connection portion and the coil end connected to the coil endconnection portion by winding are joined by arc welding.
 6. Thebrushless motor according to claim 3, wherein the terminal has a portionprotruding outward of a contour of the core or of an edge of the coil asviewed in an axial direction of the motor coil, the protruding portionbeing at a position different from a coil end connection portion.
 7. Thebrushless motor according to claim 3, wherein the metal exposure surfaceof the terminal is positioned near the ring part of the core.
 8. Thebrushless motor according to claim 3, wherein the metal exposuresurfaces of the plurality of terminals are arranged substantially atequal distances from a center of the core.
 9. The brushless motoraccording to claim 3, wherein the terminal is held by the core, and aportion between a portion held by the core and a portion for connectingthe end of the coil is bent in an axial direction of the motor.
 10. Thebrushless motor according to claim 3, wherein the terminal has a portionformed perpendicularly to a motor shaft, the portion connecting the endof the coil by winding.
 11. The brushless motor according to claim 3,wherein the power supply terminal is placed on a position correspondingto an arc welded junction of the coil end in the terminal, and the arcwelded junction is resistance-welded to the power supply terminal. 12.The brushless motor according to claim 3, wherein the terminal is madeof a copper alloy.
 13. The brushless motor according to claim 3, whereinan arc welded junction is placed outward of a contour of the core or ofan edge of the coil as viewed in an axial direction of the motor.
 14. Amethod of manufacturing a brushless motor, characterized by comprisingthe steps of: winding a coil around a core; connecting an end, of thecoil to a terminal by winding, the terminal being composed of a metallicmember; connecting an earth electrode for welding to a metal exposuresurface of the terminal; and joining by arc welding a portion on whichthe end of the coil is connected to the terminal by winding.
 15. Amethod of manufacturing a brushless motor, characterized by comprisingthe steps of: arranging a plurality of terminals radially and connectingthe terminals via a connecting member; overlaying the terminal on asurface of a salient pole on a core having a ring part and a pluralityof the salient poles extending radially from the ring part; winding acoil so as to bind the salient pole and the terminal; connecting an endof the coil to the terminal by winding; connecting an earth electrode tothe connecting member and joining by arc welding a portion on which theend of the coil is connected to the terminal by winding; and cutting andremoving the connecting member.